Twice the difference of a number and 10 is greater than -23 use the variable y for the unkown number

The above statement means:
Twice [the difference of a number and 10] is greater than -23.

Let y be the "number" or the unknown value.
In numerical form:
2 × ( y - 10 ) > -23
{Expand the inequality}
2y - 20 > -23
{Make y the subject of inequality. Add 20 on both sides of inequality}
2y > -3
{Divide both sides of inequality by 2}
y > -1.5

Hope this helps! :)